This invention relates to a grinding bar to be mounted on a dental hand piece and used for grinding or treating a tooth.
In odontotherapy, a dental hard tissue broken by Streptococcus mutans or the like is ground by the use of a diamond bar.
As such a diamond bar, various types are available according to the purpose, and those shown in FIGS. 8, 9 and 10, for example, are known.
FIG. 8 shows a conventional small-sized round type diamond bar. This diamond bar comprises a shank part 1 to be mounted on a hand piece, a neck part 2 continued to the shank part 1 and reduced in diameter toward the tip in a tapered shape, a tip spherical part 3 continued to the neck part 2, and a grinding part 4 formed by fixing diamond particles to the whole circumference of the spherical part 3.
FIG. 9 shows another conventional diamond bar, which comprises a shank part 5, a tapered part 6 continued to the shank part 5 and having a conical part 6a at the tip, and a grinding part 7 formed by fixing diamond particles to the circumferential surface of the tapered part 6.
FIG. 10 similarly shows a further conventional diamond bar, which comprises a shank part 8, a short tapered neck part 9 provided continuously to the shank part 8, a round bar-like shaft part 10 connected to the neck part 9 and smaller in diameter than the shank part 8, and a grinding part 11 formed by fixing diamond particles to the circumferential surface of the shaft part 10.
The diamond bars as conventional grinding bars have the following disadvantages.
In the bar shown in FIG. 8, the comprehensive orientation of preciseness, safely, centripetal property and the like is insufficient. Namely, the contact surface to tooth of the grinding part 4 is unstable because of the spherical shape, so that an extremely narrow treatment part such as a fine fissure in a crown part or the like cannot be precisely caught. Particularly, the grinding part 4 often slips and moves on a hard tooth surface in grinding to grind an extra part other than the part requiring the treatment.
This problem cannot be solved only by simply minimizing the spherical diameter.
In the positioning of the grinding part 4 to a treatment portion, an extra force is applied to the fingers holding a hand piece in order to prevent the slippage or movement caused by the spherical shape of the diamond bar, and this gives a psychologically large stress to dentists.
In the diamond bar having the spherical grinding part 4 as shown in FIG. 8, it is difficult to feel the difference between a carious part and a non-carious part by the fingers in the grinding of a tooth because the dental hand piece must be operated with a strong force applied to the fingertips as described above, causing the problem of the difficulty in precisely judging the grinding quantity.
In a sound dental hard tissue, the enamel Knoop hardness is 5.5, but the hardness is successively reduced according to the progress of caries.
Thus, if the grinding part can precisely catch and grind a treatment position without movement, dentists can be released from the psychological stress and clearly feel the difference in hardness through their fingerprints.
In the diamond bars shown in FIGS. 9 and 10, the grinding parts 7 and 11 cannot precisely catch a small treatment part because of their large outer diameters and axial lengths, and this introduces the danger of grinding an extra part.
Particularly, the visual field from the outside of the oral cavity to the inside is obstructed to make the treatment of a tooth difficult, resulting in the grinding of the tooth in an unnecessary wide area.
These bars are basically used for partially or entirely replacing the tooth crown with metal or ceramics, and it is regarded that the grinding of a sound crown cannot be avoided for the purpose.
In the treatment of a partial carious part between adjacent teeth, the grinding parts 7 and 11 hardly reach the limited carious part between the teeth because of the large tip diameters thereof, and the difficulty of orientation increases the danger of excessively grinding the teeth.
Accordingly, although a dental physic based on the idea that the invasion to a dental hard tissue should be minimized has been proposed in the international dental field, the conventional bars cannot satisfy this proposal.
The present invention thus has an object to provide a grinding bar capable of removing only an affected part of a minute range with a minimum grinding by allowing a grinding part, when put on the treatment part of a tooth, to stably stay in a point of a designated treatment part and perform a continuous grinding, and further surely and easily grinding and treating only a carious part by sufficiently ensuring the visual field from the outside of the oral cavity to the inside so as to easily catch the difference in hardness of dentine.
To attain the above purpose, the present invention provides a grinding bar to be mounted on a hand piece and used for grinding a tooth, comprising a shank part to be mounted on the hand piece, a tapered neck part provided continuously to the shank part, a rod part provided continuously to the neck part and more slender than the neck part, and an arrowhead-like or separate piece-like grinding part formed by fixing diamond particles to the tip of the rod part.
The grinding part is formed in outer diameters ranging from 0.4 to 0.6 mm, lengths ranging from 0.4 to 0.6 mm, and tip conical angles ranging from 60 to 120xc2x0. The grinding part 15 is preferably formed so as to have an outer diameter of 0.47 mm, a length of 0.47 mm, and a tip conical angle of 90xc2x0.
The rod part is preferably formed of a single tapered shaft having a taper converged to the tip.
The rod part may be formed of a shaft having a taper converged to the tip and a straight shaft continued to the shaft.
The rod part may be formed of a single straight and slender shaft.